Medical treatment often requires the administration of a therapeutic agent (e.g., medicament, drugs, etc.) to a particular part of a patient's body. As patients live longer and are diagnosed with chronic and/or debilitating ailments, the likely result will be an increased need to place even more protein therapeutics, small-molecule drugs, and other medications into targeted areas throughout the patient's body. Some maladies, however, are difficult to treat with currently available therapies and/or require administration of drugs to anatomical regions to which access is difficult to achieve.
A patient's eye is a prime example of a difficult-to-reach anatomical region, and many vision-threatening diseases, including retinitis pigmentosa, age-related macular degeneration (AMD), diabetic retinopathy, and glaucoma, are difficult to treat with many of the currently available therapies. For example, oral medications can have systemic side effects; topical applications may sting and engender poor patient compliance; injections generally require a medical visit, can be painful, and risk infection; and sustained-release implants must typically be removed after their supply is exhausted (and generally offer limited ability to change the dose in response to the clinical picture).
Another example is cancer, such as breast cancer or meningiomas, where large doses of highly toxic chemotherapies, such as rapamycin, bevacizumab (e.g., Avastin), or irinotecan (CPT-11), are typically administered to the patient intravenously, which may result in numerous undesired side effects outside the targeted area. Other examples of difficult-to-reach anatomical regions for drug delivery include the knee, where drugs often have difficulty penetrating the avascular cartilage tissue for diseases such as osteoarthritis, the brain, and the spine.
Methods that use an implantable drug delivery system, which may include a refillable drug reservoir, a cannula for delivering the drug, etc., generally allow for controlled delivery of pharmaceutical solutions to a specified target. This approach can minimize the surgical incision needed for implantation and typically avoids future or repeated invasive surgery or procedures. In ocular applications, implantable devices sometimes utilize a passive mechanism for drug delivery, in which drug is pumped out when, for example, a finger is pressed on the drug reservoir. This may, however, render the control of the administered drug dosage problematic. In addition, the fabrication of such devices may require cumbersome and expensive hand-assembling work. Electrolysis-driven implantable MEMS drug-delivery devices are also known, but may be rigid and therefore risk damage to the site of implantation (particularly where delicate (e.g., ocular) tissue is involved).
A need exists, therefore, for improved implantable drug-delivery devices and methods of manufacture.